This invention relates generally to a process for regulating the NH.sub.3 content of an organic liquid which is used as a physical scrubbing agent in a process for absorbing sour gases from gaseous mixtures and which is freed from the absorbed gaseous components after scrubbing and reused in the process circuit. The invention also relates to apparatus for implementing the process.
To produce refined gases from crude gases, the sour components, such as CO.sub.2, H.sub.2 S and COS must be eliminated from the crude gases. Alcohols, glycols and ethers are known to be suitable for use in such a process. The methanol-scrubbing process has proven to be especially effective. In that process, the sour gases are eliminated with methanol under temperatures to below -70.degree. C. and pressures up to 80 bar.
The crude gas which has to be scrubbed often contains traces of ammonia which become concentrated in the methanol because of its high solubility in methanol. Such concentrations of ammonia can be desirable as explained in German Pat. No. DE OS 27 59 123. The German Patent discloses a known process in which ammonia is added in small amounts, i.e., 0.05 to 0.5 weight-%, to a physical scrubbing agent such as methanol or ethanol. The resultant mixture of scrubbing agent and ammonia produces a combined physical-chemical scrubbing activity which reduces the amount of scrubbing agent which must be used.
However, the above described process can only be used effectively if the ammonia concentrations can be kept constant and can be prevented from reaching excessive levels. If the concentration of ammonia in methanol becomes excessive in the presence of carbon dioxide, solid secretions of ammonia carbaminate can be formed in the pipelines and/or the desired temperature distribution in the system can be impaired by the reaction temperature of NH.sub.3 with the sour gas components. Both of those factors can seriously disturb the scrubbing process.
German patent application No. P 30 36 936 describes a process for eliminating ammonia from methanol by means of an ion exchanger. One disadvantage with that process is that the apparatus needed for periodical regeneration of the ion exchanger is large. A further disadvantage is that there are additional accumulations of methanol-water mixture and waste water.